Field of the Invention
The present invention relates to an image forming apparatus, e.g., a copying machine or a printer.
Description of the Related Art
An electrophotographic image forming apparatus includes a photosensitive member, a charging device configured to charge the photosensitive member, an exposure device configured to expose the charged photosensitive member to form an electrostatic latent image, and a developing device configured to develop the electrostatic latent image with a developer. The image forming apparatus is configured to transfer an image onto a sheet, and to then cause a fixing device to fix the image to the sheet by heat and pressure.
In this case, for example, a streak-like image (hereinafter referred to as “vertical streak image”) may appear in the image formed on the sheet due to a stain of the exposure device, coating unevenness of the developer caused by the developing device, a scratch on a surface of the photosensitive member, or the like. For example, an image forming apparatus described in U.S. Pat. No. 7,583,408 is configured to form a measurement image on an image bearing member, and to determine whether or not an abnormality has occurred in the image formed by the image forming apparatus based on a result of detecting the measurement image by a sensor.
However, the image forming apparatus described in U.S. Pat. No. 7,583,408 is unable to determine that an abnormality has occurred when, for example, the abnormality has occurred in a transfer portion configured to transfer the image onto the sheet. Therefore, the present invention has an object to appropriately determine that an abnormality has occurred in a component of the image forming apparatus.